Control arrangement for automatically defrosting a refrigerator

ABSTRACT

A control arrangement for automatically defrosting a refrigerator in which a normally open bi-metal switch is arranged in the circuit of the motor driving the compressor of the refrigerator. The bi-metal switch closes upon heating thereof by a resistor arranged adjacent thereto. The resistor is arranged in a control circuit in series with a normally straight bi-metal strip arranged adjacent the evaporator of the refrigerator to sense the temperature of the evaporator and the bi-metal strip curves to close the control circuit upon sensing of a temperature of about between 3*-5*C to thereby energize the resistor and cause closing of the bi-metal switch. An elongated permanent magnet cooperates with the bi-metal strip to expedite closing of the latter.

Waited States Fatent Auracher CONTROL ARRANGENENT FOR AUTOMATICALLYDEFROSTING A REFRIGERATOR Robert Auracher, Stuttgart-Stammheim, GermanyEuropaische 11.0. Canfield Co., GmbH, Gartenberg/Off., Germany Filed:Mar. 8, 1971 Appl. No.: 121,928

Inventor:

Assignee:

Foreign Application Priority Data Mar. 6, 1970 Germany ..P 20 10 717.9

US. Cl. ..62/ 156, 62/80, 62/202,

62/208 Int. Cl ..F25d 21/06 Field of Search ..62/80, 156, 202, 62/208,209

References Cited UNITED STATES PATENTS [0/1956 Shaw ..62/202 PrimaryExaminerWilliam J. Wye Attorney-Michael S. Striker ABSTRACT A controlarrangement for automatically defrosting a refrigerator in which anormally open bi-metal switch is arranged in the circuit of the motordriving the compressor of the refrigerator. The bi-metal switch closesupon heating thereof by a resistor arranged adjacent thereto. Theresistor is arranged in a control circuit in series with a normallystraight bi-metal strip arranged adjacent the evaporator of therefrigerator to sense the temperature of the evaporator and the bi-metalstrip curves to close the control circuit upon sensing of a temperatureof about between 35C to thereby energize the resistor and cause closingof the bi-rnetal switch. An elongated permanent magnet cooperates withthe bi-metal strip to expedite closing of the latter.

7 Clains, 2 Drawing Figures COMM/V567? CGMWESSZZ? ram/e PATENTEUAPR1 0%3,726,105

SHEET 1 OF 2 FIG] INVI-LN'IOR: none/1r 1402401 5/1 CONTROL ARRANGEMENTFOR AUTOMATICALLY DEFROSTING A REFRIGERATOR BACKGROUND OF THE INVENTIONThe present invention relates to a control arrangement for automaticallydefrosting of refrigerators.

In modern refrigerators there are two evaporators provided, namely anevaporator for the main compartment of the refrigerator and anevaporator for the freezer compartment.

In order to prevent accumulation of ice on the evaporator of the maincompartment, the letter is provided with a heater which defrosts thisevaporator during the time it is not in operation. Nevertheless, whenthe time periods during which the evaporator is not in operation are tooshort it is possible that ice will accumulate on the evaporator of themain compartment.

SUMMARY OF THE INVENTION It is an object of the present invention toovercome this disadvantage of refrigerators known in the art and topositively prevent accumulation of ice on the evaporator in the maincompartment of the refrigerator.

With this object in view the present invention mainly comprises acontrol arrangement for automatically defrosting a refrigerator which asusual comprises an evaporator for cooling the main compartment of therefrigerator, a compressor connected to this evaporator and an electricmotor for driving the compressor, and the control arrangement of thepresent invention comprises an electrical circuit for energizing themotor, normally open bi-metal switch means in this circuit constructedto close the circuit upon heating of this bimetal switch to a firstpredetermined temperature, resistor means adjacent the bi-metal switchfor heating, during passage of current therethrough, the bi-metal switchto close the latter, control circuit means connected to the resistor,and second normally open bimetal switch means arranged adjacent the mainevaporator and sensing the temperature of the latter in which thisbi-metal switch means is constructed to close upon sensing a secondpredetermined temperature to thereby energize the resistor.

In other words, the aforementioned second bi-metal switch means areconnected to the evaporator of the main compartment of the refrigeratorand senses the temperature of this evaporator. The second bi-metalswitch closes when for instance a temperature of 3 5C is reached andclosing of this second bi-metal switch means energizes the resistor.When however the temperature sensed is for instance under 0C, or atanother value for which the second bi-metal switch is constructed, thenthe aforementioned resistor is not switched on, that is, the contacts ofthe first mentioned bi-metal switch in the main circuit of therefrigerator remain spaced from each other and the evaporator is notoperated. However, if current passes through the resistor then thebi-metal springs of the first-mentioned bi-metal switch means are heatedin a known manner and the contacts close, that is, the machine operatesas long until the desired temperature in the main compartment isreached. Thereafter, the aforementioned described cycle is repeated.

An additional feature according to the present invention is thearrangement of a magnet strip adjacent to the bi-metal strip of theabove-mentioned second bimetal switch means. This magnet strip isarranged at a distance from the bi-metal strip of the second bi-metalswitch means in such a manner that the magnet strip will not influencethe operation of the bi-metal strip of the second bi-metal switch meanswhen this bi-metal strip is in substantially straight condition. Inother words, the magnet will become active only when the bimetal stripwith its contact at one end thereof slightly curves toward the fixedcontact arranged opposite the contact on the bi-metal strip. Themovement into the closed position of the two contacts will then occursuddenly with a snap action since the bi-metal strip tends to movetowards the closing position and this movement is supported by theattraction force of the magnet.

Preferably, a permanent magnet is used for this purpose and especially aflexible magnet known per se.

The bi-metal strip of the second bi-metal switch means is constructed toclose at a predetermined temperature. This predetermined temperature ispreferably between 3 5C above zero, but evidently this switch may beconstructed to close also at other temperatures.

According to the method of the present invention, the temperature of themain evaporator of the refrigerator is constantly sensed and the motorof the compressor for feeding refrigerant into the main evaporator isonly energized if the sensed temperature is above a predeterminedtemperature and this predetermined temperature is preferably in theregion of 5C above zero.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration ofthe control arrangement of the present invention; and

FIG. 2 schematically illustrates the control arrangement connected to arefrigerator.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, thecontrol arrangement of the present invention comprises a first bi-metalswitch including the bi-metal springs 2 and 2a of which the bimetalspring 20 carries a movable contact 7 opposite of which a stationarycontact 7a is arranged, and this bimetal switch is arranged in thecircuit of a motor M which drives the compressor for furnishing arefrigerant to the main evaporator of the refrigerator. This bi-metalswitch is normally open and the contacts 7 are closed only when thisbi-metal switch is heated up to a first predetermined temperature. Aresistor l is arranged adjacent to the springs of the mentioned bimetalswitch and the resistor R is connected in series with a second bi-metalswitch comprising a bi-metal strip 3 carrying at one end thereof amovable contact 4 arranged spaced from and opposite a fixed contact 5.This second bi-metal switch is connected to the main evaporator of therefrigerator, and senses the temperature of this main evaporator. Anelongated permanent magnet 6 is arranged substantially parallel andspaced from the bi-metal strip 3.

The above-described control operate as follows:

As long as the temperature of the main evaporator sensed by the bi-metalstrip 3 will be below a predetermined temperature, for instance below Cabove zero, the bi-metal strip 3 will stay in substantially straightcondition so that the contacts 4 and 5 will be separated from eachother. When the temperature sensed by the bi-metal strip 3 rises abovethe above-mentioned temperature, the bi-metal strip 3 will curve so thatthe contact 4 carried at one end thereof will move toward the stationarycontact 5 and this movement will, after the curving has started, besupported by the attraction of the magnet 6 and therewith accelerated sothat the contacts 4 and 5 will close suddenly to thereby energize theresistor 1 which in turn will heat up the springs 2 and 2a of the mainbi-metal switch closing thereby the contacts 7 and 7a thereof toenergize the motor of the compressor which furnishes refrigerant to themain evaporator. The temperature of the main evaporator will thereby belowered which in turn will cause reopening of the contacts 4 and 5. Whenthe resistor l is not energized the main bi-metal switch will stay inthe position as shown in FIG. 2 to energize thereby the evaporatorheater or defroster so that the evaporator is defrosted while thecompressor motor is at standstill.

The magnet 6 is arranged at such a distance from the bi-metal strip 3and exerts such a force on the latter so as not to prevent the reopeningof the contacts 4 and 5. Evidently, the bi-metal strip 3 has a stripportion which is magnetizable by the magnet 6.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcontrol arrangements for automatically defrosting of refrigeratorsdiffering from the types described above.

While the invention has been illustrated and described as embodied in acontrol arrangement for automatically defrosting of a refrigerator, itis not intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the prevent invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning arrangement will and range ofequivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Control arrangement for a refrigerator including an evaporator forcooling the main compartment of the refrigerator and a compressor motor,said control arrangement comprisin an electric circuit for energizingthe motor; first norma ly open bi-metal switch means in said circuitconstructed to close said circuit upon heating of said bi-metal switchmeans to a first predetermined temperature; resistor means adjacent saidhimetal switch means for heating, during passage of currenttherethrough, said first bi-metal switch means to close the latter; andcontrol circuit means connected to said resistor and comprising a secondnormally open bimetal switch means arranged adjacent the evaporator andsensing the temperature of said evaporator, said second bi-metal switchmeans being constructed to close when the temperature of said evaporatorsensed by said second bi-metal switch means reaches a secondpredetermined temperature to thereby energize said resistor to heat saidfirst bi-metal switch to said first predetermined temperature so as toclose said first bimetal switch means.

2. A control arrangement as defined in claim 1, wherein said firstbi-metal switch means comprises two bi-metal springs and wherein saidsecond bi-metal switch means comprises a bi-metal strip carrying at oneend a movable contact and a fixed contact normally spaced from saidmovable contact.

3. A control arrangement as defined in claim 2, and including magnetmeans cooperating with said bi-metal strip for expediting closing of thelatter.

4. A control arrangement as defined in claim 3, wherein said magnetmeans is a permanent magnet.

5. A control arrangement as defined in claim 4, wherein said bi-metalstrip is normally in a substantially straight position and bends withsaid one end thereof toward said fixed contact upon sensing said secondpredetermined temperature and wherein said permanent magnet is in theform of a magnet strip extending substantially parallel to said bi-metalstrip and spaced therefrom a distance such so as not to cause closing ofsaid second bi-metal switch means when said bi-metal strip thereof is insaid straight condition.

6. A control arrangement as defined in claim 1, wherein said secondbi-metal switch means is constructed to close at a temperature of about5C above zero.

'7. Control arrangement as defined in claim 1, wherein said controlarrangement further comprises heating means for heating said evaporatorto said second predetermined temperature to thereby defrost saidevaporator, said heating means being connected to said first bi-metalswitch means to be actuated when said first bi-metal switch means is inopen position.

1. Control arrangement for a refrigerator including an evaporator for cooling the main compartment of the refrigerator and a compressor motor, said control arrangement comprising an electric circuit for energizing the motor; first normally open bi-metal switch means in said circuit constructed to close said circuit upon heating of said bi-metal switch means to a first predetermined temperature; resistor means adjacent said bi-metal switch means for heating, during passage of current therethrough, said first bi-metal switch means to close the latter; and control circuit means connected to said resistor and comprising a second normally open bi-metal switch means arranged adjacent the evaporator and sensing the temperature of said evaporator, said second bi-metal switch means being constructed to close when the temperature of said evaporator sensed by said second bi-metal switch means reaches a second predetermined temperature to thereby energize said resistor to heat said first bi-metal switch to said first predetermined temperature so as to close said first bi-metal switch means.
 2. A control arrangement as defined in claim 1, wherein said first bi-metal switch means comprises two bi-metal springs and wherein said second bi-metal switch means comprises a bi-metal strip carrying at one end a movable contact and a fixed contact normally spaced from said movable contact.
 3. A control arrangement as defined in claim 2, and including magnet means cooperating with said bi-metal strip for expediting closing of the latter.
 4. A control arrangement as defined in claim 3, wherein said magnet means is a permanent magnet.
 5. A control arrangement as defined in claim 4, wherein said bi-metal strip is normally in a substantially straight position and bends with said one end thereof toward said fixed contact upon sensing said second predetermined temperature and wherein said permanent magnet is in the form of a magnet strip extending substantially parallel to said bi-metal strip and spaced therefrom a distance such so as not to cause closing of said second bi-metal switch means when said bi-metal strip thereof is in said straight condition.
 6. A control arrangement as defined in claim 1, wherein said second bi-metal switch means is constructed to close at a temperature of about 5*C above zero.
 7. Control arrangement as defined in claim 1, wherein said control arrangement further comprises heating means for heating said evaporator to said second predetermined temperature to thereby defrost said evaporator, said heating means being connected to said first bi-metal switch means to be actuated when said first bi-metal switch means is in open position. 